Research On Landing Gear System Modeling Based On Modelica

As technology and innovations developing, multi-domain simulation has become anessential method in the design and analysis of complex systems. Modeling and simulationbased on unified multi-domain modeling language Modelica has become a new generation ofCAE technology supporting this method. This technology has come to maturity and manytypes of software have sprung up. Contemporarily, this technology is widely used in industry.Now, the domestic industrial applications of Modelica are on the trial sub stage.This paper focuses on the fields of hydraulics and mechanics, discusses some keytechnologies in multi-domain modeling and simulation in Modelica. The paper is funded bythe National High Technology Research and Development Program of China (863Program)and the Landing Gear Hard-In-Loop Simulation Platform Project of COMAC. The maincontributions of the paper are as followsFirstly, the features and principles of modeling in Modelica are introduced in this paperincluding the property of Object-Oriented, the method of declarative, the descriptions ofinterfaces and the laws of energy flow.Secondly, some technologies of components design and development are presented. Inthe field of hydraulics, every component can be assembled by3types of hydraulic elements;hence the component design becomes more convenient; Cause of the singular problem withthe traditional turbulence equation is shown together with a resolution of adding a controlvariable to modify the equation; In the field of mechanics, the paper introduces the conceptof over-determined constraints in multi-body modeling and how to drawing a virtualconnection graph. With the help of the map, connectors (or interfaces) of a multi-bodycomponent can be designed correctly; Branch events are also common in Modelicacomponents. In order to find the best form of branch, the comparison between different typesof branch events is given, together with its range of application.Thirdly, some technologies of system design and development are also issued. Thepaper summarized two kinds of ways to build and debug the systems: Core Extension andGradual Accuracy. An adjustment model is used to design and debug a3dimensionmechanical circle system. The paper discusses how to select state variables, how to set initialvalues, and how to calculate the initial values of a complex system. And then a flow chart of developing a multi-domain system model is drawn.Finally, a hybrid system of landing gear is modeled. And parameters of this model arecalibrated by characteristic experiments. From the comparison of the simulation result andthe experiment result, validation of the model can be founded.